The present invention relates generally to dispensing devices used in laboratory analysis and more particularly to syringes for dispensing liquid for use in medical and chemical analysis.
Syringes are commonly used in laboratories for dispensing precise quantities of materials. The hollow narrow gauge needles used at the syringe tips allow very exact measurement and delicate placement of materials. This same delicacy of mechanism means that the needles used can be easily damaged by chance collisions with other objects or clogged by inconsistencies in the material to be dispensed. When such needles are damaged, they must routinely be replaced.
Prior art needles are commonly glued into the glass barrel of the syringe, in which case the entire syringe must be discarded, or reworked by heating the syringe until the needle is released from the barrel. A new needle can be then be inserted and glued into place. This reworking operation can be less expensive than buying a new syringe, but requires that the damaged pieces be collected, packaged and returned to the manufacturer.
Alternatively, some prior art syringes are made with removable needles. However, these syringes usually require that a collar with machined threads be glued to the syringe barrel. The needle is usually attached to a Teflon(trademark) pad which seats against the end of the barrel at the zero line. A cap with a central aperture is then inserted over the needle, and the cap, which is typically fitted with a threaded portion, engages the threads on the collar to hold the needle securely in place. This has the advantage of allowing easy replacement of the needle, but is more expensive from a manufacturing standpoint, since extra components such as the collar and cap must be produced and provided with machined threads and physically attached to the syringe.
Another problem with a screw-on collar is that if the collar is not tightened enough, the syringe may leak at the join. At the other extreme, if too much torque is applied in an effort to prevent leaks, the glue seal between the glass and the collar can break, thus causing damage to the device and causing additional leaks.
Thus there is a need for a syringe with a replaceable needle which can be assembled to produce a liquid-tight seal without the use of costly attachment mechanisms found in the prior art.
Accordingly, it is an object of the present invention to provide a syringe with a replaceable needle, which is less prone to damage during replacement.
Another object of the present invention is to provide a syringe with a replaceable needle with a simplified joining mechanism.
A further object of the present invention is to provide a syringe with a replaceable needle which is not glued to the syringe barrel.
A still further object of the present invention is to provide a syringe with replaceable needle which does not require machining of threads on the mating parts and is thus easy to manufacture and less expensive.
An additional object of the present invention is that a flexible, two-stage needle can be used as the replaceable needle.
Briefly, one preferred embodiment of the present invention is a syringe with replaceable needle assembly, having a syringe barrel with a proximal end, a distal end, and an outer surface. The syringe barrel surrounds an internal bore having an internal diameter. A plunger assembly is inserted into the syringe barrel internal bore. A needle assembly has a sealing portion which is configured to be removably insertable into the internal bore. The sealing portion forms a fluid-tight seal with the internal bore. The needle assembly further includes a releasable locking mechanism which includes a collar having a locking flange.
A second preferred embodiment is a replaceable needle assembly, which releasably locks onto the outer surface of the proximal end of a syringe barrel. The replaceable needle assembly includes a collar, having a locking flange, which engages the outer surface of the syringe barrel, and releasably locks the replaceable needle assembly onto the syringe barrel.
An advantage of the present invention is that the needle is quickly and easily replaced without damage to the needle or the barrel of the syringe.
Another advantage of the present invention is that no glue or adhesive is required to join the parts.
A further advantage of the present invention is that no screw threads are used to join the parts, thus the device is easy and inexpensive to manufacture.
An additional advantage of the present invention is that a two-stage needle can be used in which a very narrow gauge tip portion is partially enclosed with a rigid portion which allows for less damage to the tip, while maintaining enough rigidity for precise guidance.